There are a number of systems for controlling the advancement of a strand, each system having its characteristics and limitations. In high speed production of bulked or texturized yarns, the systems for controlling the advancement of a strand to the texturizing jet can significantly affect the type of texturized yarns produced.
For example, it has been found that by locating a strand advancement control unit, which will be described later on, between the texturizing jet and the large diameter feed roll of the type of strand advancing means having a pair of coaxial multiple diameter feed rollers which are in a fixed, pre-determined position in relation to the inlet and outlet orifices of the texturizing jet, a bulky yarn having randomly located slubbed portions along the length thereof can be produced. U.S. Pat. No. 3,411,287, issued Nov. 19, 1968, describes a strand advancing means having two multiple diameter feed rollers which are in fixed in pre-determined position in relation to the inlet and outlet orifices of the fluid jet and are driven at high speed with the untexturized yarn being wrapped around and between the large diameter surfaces to feed the jet and the small diameter surfaces on the feed rollers to withdraw the yarn from the texturizing jet.
To control the amount of overfeed supplied to the texturizing unit, the yarn advancing from the large diameter feed roller is passed through a pair of rigidly located guide eyes. Intermediate such guide eyes, a third guide eye is fastened to the piston of a dual acting air cylinder. In the "rest" position the strand is permitted to pass along a straight path between the feed roller and texturizing jet through the guide eyes. The air cylinder can be energized to slowly withdraw, or deflect, the effect yarn from the straight, or primary, path and thus reduce the amount of overfeed of the effect yarn entering the texturizing jet. Then the air cylinder can be reversed to quickly move the third guide eye back to the "rest" position to permit the portion of strand accumulated, or deflected, from the primary path to enter the texturizing jet as a sudden increase in overfeed and thus produce a slubbed region along the length of the texturized strand.
In such a system a portion of the overfeed of the effect yarn is accumulated and released to produce slubbed regions along the length of the texturized yarn.
In an effort to further modify the system, the present invention provides a unit for fluidically controlling the advancement of the effect yarn entering the texturizing jet.